#19, it depends what you mean by landscape. My preference for landscape is as wide angle a lens as I can afford, neither this one (not much better than kit lens) or 50mm for me. The one I finally saved for is this one: http://www.amazon.com/Canon-EF-S-10-22mm-3-5-4-5-Digital/dp/B0002Y5WXE/ref=pd_sip24

Now I have something like $1,800 in lenses (which, honestly, ain't much since a pro would spend that much on a single lens, easy). But with the 50mm (inside, portrait, macro with an extension), the 70-200mm (outside, nature, zoom, mild action), the one above (wide angle inside, beautiful landscapes), and the kit lens (walk around, party lens with good image stabilization), I have everthing I need. Plus, they will all upgrade fine to the next body I get.

On landscapes, though, remember your crop factor before getting too attached to a focal length!

Is the 70-200 f/4 fast enough to shoot w/o IS in low-light?

#19,
Unfortunately with the 1.6x crop factor, 50mm lens is actually working as 80mm, 55mm as 88mm respectively. The narrow field of view will not be enough for landscape shots. You need a wide angle lens in the 10 to 20mm range (16 to 32mm in 1.6x crop).

somebody can correct me if i'm wrong. wide angle lens usually suffer with heavy barrel distortion. The way to correct it is through computer post proccesing, such as lightroom or Canon DPP. The advantage of DPP is it contains all the canon lens profile. With a click of a button, the barrel distortion will be easily corrected. So, if you have a 1.6x crop camera and want to get a wide angle lens for landscape shots, you should consider canon lens first.

#19 - If landscape shots is what you seek, get something with a focal length under 50mm. I've got the EF-S 10-22mm and it's a great fish-eye lens but not cheap.

#19, remember you have the option to shoot several images and "stitch" them together using Canon software. If this is your choice, then the 50mm is fine.

Or, you are too lazy to process the images, then, like other said, spend some money for a fisheye. However, you'll get distortion at some level. People post their fisheyed photos from particulat lenses everywhere. Go take a look.

Again, the 10-22 is the most wide open on the market now afak, but for average people, a Tamron or a Sigma 18-270 is the best shot. I love to have one, but I'm too cheap so I need someone eat my 50-250 first.

Thanks for the info everyone. I also just registered on POTN and i'm learning a bit more about it.

ironbadge, I've "stiched" pictures in the past using my point and shoot. again, new to the DSLR scene and just learning as I go.

again, a BIG THANK YOU to all those that posted info regarding my question.